The present invention relates to a mini-fan unit comprising a fan wheel driven by a dc motor without collector, such fan unit especially directly mounted on a printed circuit board.
Such fan units are, for example, known from German Gebrauchsmuster 295 01 695.7. The drive motor is a disk armature motor comprising an annular permanent magnetic rotor. The rotor is axially displaced relative to the stator and is arranged parallel thereto so that a planar air gap is formed between the permanent magnet and a coaxially arranged annular stator coil. The stator comprises an annular ferromagnetic plate as a magnetic ground element (back iron) for the rotor magnet. A further ferromagnetic back iron disk can be connected to the rotor itself. In this context, a ferromagnetic auxiliary arrangement for producing a magnetic auxiliary moment in cooperation with the rotor magnet is required.
The present invention therefore has the object to provide a mini-fan unit of the aforementioned kind which is especially simple, compact, and inexpensive.